| error[E0658]: the `concat` meta-variable expression is unstable |
| --> $DIR/feature-gate-macro-metavar-expr-concat.rs:3:14 |
| | |
| LL | let ${concat($lhs, $rhs)}: () = (); |
| | ^^^^^^^^^^^^^^^^^^^^ |
| | |
| = note: see issue #124225 <https://github.com/rust-lang/rust/issues/124225> for more information |
| = help: add `#![feature(macro_metavar_expr_concat)]` to the crate attributes to enable |
| = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date |
| |
| error: aborting due to 1 previous error |
| |
| For more information about this error, try `rustc --explain E0658`. |
